AspectJ question

[George Lawniczak]

I have a question for anyone out there using AspectJ. I am trying to use AspectJ in combo with JUnit to get to simulate the use of mock objects by creating a hash map in my aspect that tracks which class/method combinations are to be stubbed. The other thing I am trying to do is to specify an Exception to be thrown, in order to test how the class handles certain exceptions. Below is my advice for the exception handling:
pointcut throwException(Object target) : execution(* *.* (..) throws *Exception )&& target (target) ;
pointcut withinThis() : within(MockObject +) || target(MockObject +);
pointcut withinTestCase() : within (AspectTestCase +) || target(AspectTestCase +);

before(Object target) throws Throwable : throwException(target) && !withinThis() && !withinTestCase()
{
String key = target.getClass().getName()
+ "."
+ thisJoinPoint.getSignature().getName();
if (myHashMap.containsKey(key))
{
if (myHashMap.get(key) instanceof Throwable)
{
throw (Throwable) myHashMap.get(key);
}
}
}
I have tried to make the code generic so that basically any method that could possibly throw an exception will run this advice and check to see if the current method is designated to automatically throw the exception. I have a method called setMock(String,Object) in which the first parameter is a string in the form "Class.Method" and the second argument is an object that either specified the return value, or an Exception.
When I try to compile the code in Eclipse, I get some errors stating "can't throw checked exception at this join point..." Yet the objects all compile and the aspect get woven in, and when I run my test, it works perfectly. But I still have these nasty red X's next to my objects. Is this a bug in AspectJ, and has anyone else come across this issue. I really hope to use this aspect to greatly simplify my unit testing, and I am so close to getting it right, but I need to resolve why this is happening.

[Barry Gaunt]

George, sorry I have not seen this before. Is this question still actual?
-Barry

[Barry Gaunt]

George, the following compiles when "*Exception" in the first pointcut is changed to "Throwable". Maybe that gives you a clue (I'm using the monkey see - monkey do technique here, I'm just getting a handle on AspectJ myself . )

package george;
import java.util.*;
public aspect George {
static class Other {
void setObject(String s, Object o) throws Exception {
}
}
static class MockObject {
}
static class AspectTestCase {
}
HashMap myHashMap = new HashMap();
pointcut throwException(Object target) : execution(
* *.* (..) throws Throwable) // was *Exception
&& target(target);
pointcut withinThis() : within(MockObject +) || target(MockObject +);
pointcut withinTestCase() : within(AspectTestCase +)
|| target(AspectTestCase +);
before(Object target)
throws
Throwable : throwException(target)
&& !withinThis()
&& !withinTestCase() {
String key =
target.getClass().getName()
+ "."
+ thisJoinPoint.getSignature().getName();
if (myHashMap.containsKey(key)) {
if (myHashMap.get(key) instanceof Throwable) {
throw (Throwable) myHashMap.get(key);
}
}
}
}
 

[George Lawniczak]

Thanks for the reply. Actually I got the solution from AspectJ in Action. What you need to do is to throw and Exception like MockException that is a runtime exception, but wrapping the intended exception. Then another aspect can trap the MockException, call the getCause() method then within that aspect, set up an if-then block to actually throw the original exception. That solved my problem of making my mock object aspect more generic.

[HS Thomas]

Hi George,

--------------------------------------------------------------------------------
I have a question for anyone out there using AspectJ. I am trying to use AspectJ in combo with JUnit to get to simulate the use of mock objects by creating a hash map in my aspect that tracks which class/method combinations are to be stubbed.

May I pick your brains and ask where did you get the idea of using AspectJ and JUnit and what was the motivation ? The possibilities are endless.
regards

[George Lawniczak]

Originally posted by HS Thomas:
Hi George,


May I pick your brains and ask where did you get the idea of using AspectJ and JUnit and what was the motivation ? The possibilities are endless.
regards

I found several articles on the Internet:
Test flexibly with AspectJ and mock objects
http://www-106.ibm.com/developerworks/java/library/j-aspectj2/?open&l=007,t=gr

Virtual Mock Objects using AspectJ with JUNIT
http://www.xprogramming.com/xpmag/virtualMockObjects.htm
IMHO this is where AspectJ is going to get the most use. I see using this framework not just for testing, but also for creating quick prototypes and demo applications as well.
-George